It is well known that preheating the fuel used in an internal combustion engine improves the efficiency of the engine. Further, preheating the fuel typically used in a diesel engine can avoid serious fuel flow problems well known to occur in cold weather environments.
Diesel fuel, and in particular the No. 2 fuel oil typically burned by the engines of over-the-road trucks, can congeal or "wax" in the cold weather regularly experienced during the winter months in the northern states of the United States and in Canada. The jelling or waxing of fuel can shut a diesel engine down, necessitating the towing of the vehicle to a repair facility where the fuel tank must be heated to alleviate the problem. The expense of towing and downtime can be substantial.
A number of methods and devices have been developed in an attempt to solve the problem of congealing fuel oil in cold weather. One method has been to install a heater in the fuel line. U.S. Pat. No. 3,929,187 discloses a device which utilizes this method. However, this method does not solve the problem of fuel oil congealing within the fuel tank itself before it even gets into the fuel line. Another method is to install a heater in the fuel tank. U.S. Pat. No. 4,237,850 discloses a device which utilizes this second method. The device disclosed in this patent has two primary disadvantages. One, while the fuel can be heated in the tank to a temperature above that at which it "waxes", it is not necessarily heated to a temperature which will prevent it from congealing in the fuel line in extremely cold weather, because of the volume of fuel which must be heated in the tank which is usually directly exposed to the cold outside air temperatures. Second, the device disclosed in this patent requires an access opening which must be cut/formed into the top of the fuel tank prior to installation of the device.
Therefore, it is a principal object of the present invention to provide a system for preheating diesel fuel in the fuel tank to a temperature above that at which the fuel would normally congeal.
It is a further object of the present invention to provide a system for preheating the diesel fuel leaving the fuel tank to a temperature which is sufficiently higher than the temperature at which the fuel would normally congeal such that the fuel cannot jell in the fuel line between the fuel tank and the diesel engine to which it is supplied.
It is yet another object of the present invention to provide a system for preheating the fuel in the fuel tank of a diesel engine-powered vehicle or machine which includes a heat exchanger which can be installed through and secured in the opening normally provided in such a fuel tank for the installation of a fuel level gauge.